1. Field of the Invention
This invention generally relates to a label printer for printing labels, such as self-adhesive labels. Such a printer can have a pressure roller and, corresponding to the pressure roller, a print head which has printing elements for printing on the label material. The print head can be mounted on a support which can be biased towards the pressure roller to engage the pressure roller, by means of a compression spring mounted on a base plate and engaging the print head support. At least the spring base plate is mounted so that it can rotate on a bearing shaft which is preferably parallel to the pressure roller. In addition, there can also be a locking element which can be non-rotationally connected to the bearing shaft, which locking element can be moved into a locking position in a latching locator of the spring base plate to maintain the spring base plate from turning on the bearing shaft.
2. Background Information
A similar printer of the type described above and invented by the present applicant is disclosed in German Patent No. 41 39 891A1. The thermal print head disclosed therein is fastened on a support, which support is mounted rotationally on a bearing shaft which runs parallel to the counterpressure roller. The application force of the print head against the counterpressure roller is defined by a compression spring, wherein the opposite end of which the spring is in contact with a spring base plate. The spring base plate is also rotationally mounted on the bearing shaft. The spring base plate is stopped by a hinged block, or key, which is non-rotationally connected to the bearing shaft and is oriented parallel to the bearing shaft. The spring base plate is pivoted on the bearing shaft when it is necessary to replace the print head with a new or different print head, or when it is necessary to replace the medium which is being printed because it has run out, or when it is necessary to replace the medium being printed with another type of medium.
One disadvantage of such a configuration is that the key is on one hand relatively complex, time-consuming and expensive to manufacture, and on the other hand, on account of its orientation is undesirably deformed as soon as significant azimuthal shear forces are exerted on the plate.